1. Field of the Invention
The invention relates to a device for switching activation of a hydraulic valve play equalization element for optional setting of a maximal stroke or a zero stroke on a valve of an internal combustion engine.
2. The Prior Art
The invention is preferably used for a hydraulic valve play equalization element such as described in German Patent Application No. DE 10 2007 033 757 A1. In this connection, the valve drive for an internal combustion engine consists of a drag lever impacted by a cam. One end of the lever is connected with a gas exchange valve, and the other end of the lever is mounted on a valve play equalization element. Optionally, a maximal stroke or a minimal stroke is adjusted on the valve of the internal combustion engine, by turning the support of the drag lever on or off by the hydraulic play equalization element. In order to be able to implement a zero stroke, i.e. a cylinder shut-off, or a minimal valve stroke in the case of this valve drive, the support of the drag lever on the valve play equalization element is unlocked. Unlocking and locking of the valve play equalization element takes place by way of a rotating switching ring that surrounds the housing and is connected with balls disposed in bores in the housing, which balls can be displaced by the switching ring. For locking, the balls are pressed into a groove disposed in the guide, by the inner wall of the switching ring during rotation of the switching ring, so that the housing with the guide situated in it is locked in place by the balls. On the inside of the switching ring, recesses are disposed that are brought into agreement and aligned with the bores in the housing, for unlocking the housing relative to the guide, by rotating the switching ring, so that the balls are pressed into the recesses of the switching ring. In this connection, an adjustment device for activating the switching ring was not described.
A valve drive for internal combustion engines is also described in German Patent Application No. DE 197 30 814 A1, in which a switching means for optional switching of the stroke valve between a maximal stroke and a zero or minimal stroke is disposed in the support element of the drag lever. The switching means consists of a rod that can be displaced by a displacement means, by way of which rod the support element is locked or unlocked.
A disadvantage of this solution is the complicated guidance and placement of the switching means in the housing of the internal combustion engine.
European Patent Application No. EP 1 493 902 A1 describes a device for valve shut-off, in which the valve switching is activated by way of a controlled oil feed. In this connection, the oil feed is regulated by rotating a control piece. Rotation of the outer control piece takes place by way of a gear rack that engages an outer gearing disposed on the control piece.
A disadvantage of this solution is the great effort for rotation of the control piece. Furthermore, it is also difficult to implement individual shut-off of individual valves.